A. Field of the Invention
The invention relates to a closure plug and, more particularly, to a closure plug which opens to provide ready passage of a conduit therethrough and which thereafter closes tightly on withdrawal of the conduit.
B. Prior Art
In the manufacture of insulated closures, such as refrigerator and freezer cabinets, it is a common practice to fabricate the closure in the form of a rigid hollow shell with one or more access openings and subsequently to fill the shell through the openings with an insulative resin foam such as polyurethane foam. The foam is typically introduced into the shell in an uncured state through a foam nozzle or conduit and then allowed to cure and solidify within the shell. In order for the foam to fill the shell completely, air trapped in the shell and gaseous agents accompanying the foam must be allowed to vent through the opening during filling. However, once the shell is filled, it is desirable to seal the opening to prevent leakage of the foam and to maintain a positive foam pressure within the shell during curing. Closure plugs of various designs have heretofore been used for this purpose.
One such closure plug is described in U.S. Pat. No. 3,739,963. This plug is designed to be snapped in an access opening in the closure shell being filled. The main portion of the plug has a plurality of slits defining a plurality of resilient flaps which normally occupy a common plane and seal the opening. The plug also includes a liner of a flexible material which is also slit but at such locations that the slits in the liner are offset from the slits in the main portion. With this construction, the flaps and liner can be deformed to allow the passage of the foam nozzle or conduit through the plug for the introduction of the resin into the shell. After withdrawal of the conduit, the flaps and liner return to their normal positions to seal the opening and prevent leakage of the foam.
Closure plugs of the type described in the above patent are generally fabricated using at least two different plastic materials, one for the main portion of the plug, and the other for the flexible inner liner. In order for the slits in the main portion of the plug to be offset from those in the liner, the slits must be cut prior to securing the main portion and liner together. Finally, the main portion and liner must be suitably secured together typically by using a layer of adhesive therebetween. Each of these steps adds to the complexity and cost of manufacturing the plugs.